Development and evaluation of composite insulated beams
Decline in supplies of old growth wood coupled with increased demand for structural timber by the construction industry led to creation of engineered timber products (EWPs) comprising wood waste. The author designed, fabricated and tested composite insulated beams (CIBs) which are foam filled sandwich panels constructed from EWPs. CIBs in many cross-sections and materials were limit-tested for structural performance, long-term durability, thermal and dynamic behaviours. Varaiation in material properties was overcome by statistical sorting of beams with different stiffness. Some types of CIB were found to provide better structural performance than equivalent timber and glulam I-beam sections and the CIBs maintained a high strength to weight ratio. A parametric study based on Eurocode 5 determined the governing design criteria for CIBs. The study showed that in identical loading conditions CIBs offer longer spans than conventional EWP I-beams, together with lower beam depths for similar spans. Injected polyurethane foam improved long-term durability, bearing capacity and damping ratio of beams, but reduced thermal loss and reduced weakening effect of a web opening on shear strength of beams.